This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The kinase domain P4, transfers a phosphate group to the conserved histidine residue in the P1 domain of histidine kinase CheA. In this work we aim to determine the interaction between these two domains. Previous experiments have established that P1 domains are widely separated from each other and have considerable degree of freedom. In order to resolve the associated long distances, we use deuterated proteins from E.coli.